ASTM A350 LF2 Class1

[SiVxyz]

I need to know what type of Charpy value I could get after normalizing and tempering ASTM A350 LF2 Class1. I tried normalizing only and results are just passing to minimum.

Thank you

 

[metengr]

You need to temper to really improve the CVN impact values from a minimum of 15 ft-lbs at -50 deg F.

 

[stanweld]

Double normalizing and tempering will also improve Charpy absorbed energy at -50 F.

 

[SiVxyz]

Thank you for this information. Does anybody have an idea of what type of Cv value we could get after tempering at 1000°F, 1100°F, etc.

 

[metengr]

SiVxyz;
Why are you so concerned with the value? As long as you meet the minimum requirement, this is all that is necessary. Also, the minimum tempering temperature is specified in the ASTM specification at 1100 deg F. Review the specification.

 

[SiVxyz]

Yes, you are right. I should have wrote 1100°F, 1125°F, ... The idea is to get Cv -vs- Tempering T° and UTS -vs-Tempering T° relationships because I don't want to fall below UTS min.

Thank you

 

[SiVxyz]

Normalized ASTM 350 LF2 CL1 was tempered at 1100°F for 2 hours. The impact values obtained are half of what normalized only gave, falling below minimum ASTM requirements. I am surprized because I was expecting an improvement. Is it possible that temper embrittlement occured although the cooling wasn't slow. I wonder what effects will have the following on the impact properties:

Double tempering at same temperature
Increase tempering temperature

Thank you

 

[stanweld]

Advise checking full chemistry for niobium and vanadium, which may be used in fine grain melting. These two constituents may produce secondary carbides at the tempering temperature and decrease absorbed energy values.

 

[metengr]

Did you meet the LF2 Class 2 impact requirements at -0 Deg F instead of the Class 1 at -50 deg F? If you did not meet the Class 1 impact requirements, it could be that you did not have a fine grained structure or problems ocurred during normalizing or as stanweld mentioned.

 

[SiVxyz]

I found in letterature (as stanweld also said) that grain refinement for low carbon steel 0.18%C-1%Mn (which is close to A350) can be achieve by double normalizing. Second normalizing is suggested at T° slighly over Ac3 (1500-1525°F). I might try that since ASTM A350 does not prescribe any normalizing T° neither forbit double normalizing.